**3.3 The double resonator antiresonant reflecting optical waveguide sensor**

Both the SL-ARROW and DL-ARROW are formed to generate the ARROW effect in the fiber optic sensor. However, many long-standing challenges still exist in the ARROW-based fiber sensor, such as serious temperature cross-sensitivity [12]. The ambient temperature change can also modulate the resonance condition of ARROW, making a decrease of the measurement accuracy for both SL-ARROW and DL-ARROW. Therefore, the double resonator ARROW (DR-ARROW) has been investigated to solve the temperature cross talk in the fiber sensor. In this section, the biosensor fiber sensors are taken as examples, and the working principle of the DR-ARROW is introduced [12].

The in-line fiber optofluidic waveguide biosensors possess both enhanced sensing performance and ultracompact size, which have been widely used in the lab-infibers chemical and biological sensing [12]. In-line fiber biosensors possess many distinctive advantages such as high sensitivity, compact size, and immunity to electromagnetic interference [28]. Here, a biosensor based on DR-ARROW for the detection of interferon-gamma (IFN-γ) concentration has been introduced. The schematic construction of the proposed biosensor sensor is given in **Figure 8**. In the proposed sensor, a HCF was employed as the sensing fiber, as shown in **Figure 8(a)**. The HCF consists of an air octagon core, an air-ring cladding with eight holes, and a silica cladding. The NaCl solution was filled into a cladding hole with a length of 10 cm through the capillary force by immersing the remaining SMF into the NaCl

*(a) The cross section of the HCF. (b) The cross-section of the NaCl-infiltrated HCF. (c) The schematic diagram of the dual-optofluidic waveguide ARROW [12].*

solution for �48 h, as shown in **Figure 8(b)**. The liquid sample could be also pumped out of the hole through the other microchannel, as an outlet, as shown in **Figure 8(c)** [12].

The cross-sectional schematic diagram of the optical fiber biosensor is shown in **Figure 9(a)**, which can be described by a DL-ARROW model [12]. Due to the infiltration of IFN-γ or NaCl with high RI in the cladding of HCF, the guided light will reflect at the two interfaces of the cladding, thus forming a Fabry-Pérot resonator, as shown in **Figure 9(b)**. Therefore, an ARROW is formed in HCF. However, due to two different infiltration materials, the IFN-γ solution and the NaCl solution, two ARROWs appear in HCF. At the wavelength of 1550.38 nm, the resonance condition of the ARROW for the optofluidic waveguide is achieved [12]. On the other hand, at the wavelength of 1557.86 nm, the resonance condition of the ARROW for the NaCl-infiltrated channel is achieved [13]. Hence, there are two resonance dips corresponding to two materials, which can be expressed as Eqs. (6) and (7) [12, 13]:

$$\lambda\_o = \frac{2\left(d\_{op}\sqrt{n\_{op}^2 - n\_{air}^2} + d\_{cl}\sqrt{n\_{silica}^2 - n\_{air}^2}\right)}{m} \tag{6}$$

biosensor with temperature compensation is formed by interrogating and inquiring the wavelength interval between the two resonance dips of the dual-optofluidic

The biosensor of DR-ARROW was also tested [12]. The corresponding transmission spectra, **Figure 1A** is shown in Appendix [12]. The transmission spectrum of the ethanol and NaCl infiltrated the dual-optofluidic waveguide ARROW biosensor, **Figure 1A(a)** is shown in Appendix [12]. There are two resonance dips in

1550.86 nm are consistent with the theoretical predictions of the ethanol-infiltrated Fabry-Pérot cavity (1545.78 nm) and the NaCl-infiltrated Fabry-Pérot cavity (1550.38 nm) [12]. Therefore, there will be two resonance dips if the two materials infiltrated Fabry-Pérot resonators at the same time. Different concentrations of ethanol solution are injected into the optofluidic waveguide channel, and the corresponding RI changes from 1.3568 to 1.3622 RIU. When the temperature is 20° C, the wavelength shift of the ARROW of dual-optofluidic waveguide with different RIs, **Figure 1A(b)** is shown in Appendix [12]. The wavelengths of two resonance attenuations for different RIs, **Figure 1A(C)** is shown in Appendix [12]. In addition, the wavelength spacing of the two resonance dips, **Figure 1A(d)** is shown in Appendix [12]. In this experiment, if the resolution of OSA is 0.02 nm, the

In addition, the effect of temperature on the biosensor was investigated by experiments [12]. The transmission spectra of the biosensor at different temperatures from 20 to 80°C are shown in **Figure 10(a)** [12]. At different temperatures, the two resonance decays shift to longer wavelengths at the same time. However, due to the same temperature response of the two ARROWs, the wavelength interval is maintained at a standard change of 0.02 nm, as shown in **Figure 10(b)** [12]. Hence, the dual-optofluidic waveguide ARROW biosensor is not sensitive to

Most of the ARROW-based fiber sensors only rely on the working principle of the ARROW. In recent years, the fiber optic sensor of the hybrid antiresonant reflecting optical waveguide (H-ARROW) has been researched. Besides the ARROW, another mechanism was also formed in the fiber, making a hybrid

*(a) Wavelength shifts at different temperature from 20 to 80°C and (b) wavelength of resonance dips and the*

the wavelength range of 1525–1565 nm. The resonance dips at 1545.58 and

sensitivity of RI response can reach �1413 nm/RIU [12].

temperature by interrogating the wavelength interval [12].

**Figure 10.**

**21**

*wavelength interval [12].*

**3.4 The hybrid antiresonant reflecting optical waveguide sensor**

flow waveguide ARROW [12, 13].

*DOI: http://dx.doi.org/10.5772/intechopen.93345*

*The Antiresonant Reflecting Optical Waveguide Fiber Sensor*

$$\lambda\_n = \frac{2\left(d\_{op}\sqrt{n\_{na}^2 - n\_{air}^2} + d\_{cl}\sqrt{n\_{silica}^2 - n\_{air}^2}\right)}{m} \tag{7}$$

where *m* is the resonance order, *λ<sup>o</sup>* and *λ<sup>n</sup>* are wavelengths of resonance dips for IFN-γ and NaCl solution, *dop* and *dcl* are diameters of the hole and thickness of the silica cladding, and *nair*, *nop*, *nna* and *nsilica* are RIs of the core, IFN-γ solution, NaCl solution, and silica, respectively.

Due to the change of RI in the optofluidic waveguide [12], the immunoreaction between the aptamer and the IFN-γ could modulate the wavelength of the resonant dip for the IFN-γ infiltrated ARROW. However, the resonant wavelength dip is fixed because of the channel independence of NaCl-infiltrated resonator. On the other side, due to the similar thermos-optical coefficients of the NaCl and IFN-r, the wavelength shifts of two resonance dips corresponding to two ARROWs have the same response to the temperature fluctuation [12]. The response of the two resonance attenuation wavelength shifts corresponding to the two ARROWs to temperature fluctuation is the same. Therefore, a dual-optofluidic waveguide ARROW

**Figure 9.** *(a) Diagram of the dual-optofluidic waveguide ARROW and (b) the Fabry-Pérot resonator [12].*

*The Antiresonant Reflecting Optical Waveguide Fiber Sensor DOI: http://dx.doi.org/10.5772/intechopen.93345*

solution for �48 h, as shown in **Figure 8(b)**. The liquid sample could be also pumped out of the hole through the other microchannel, as an outlet, as shown in

*Electromagnetic Propagation and Waveguides in Photonics and Microwave Engineering*

**Figure 9(a)**, which can be described by a DL-ARROW model [12]. Due to the infiltration of IFN-γ or NaCl with high RI in the cladding of HCF, the guided light will reflect at the two interfaces of the cladding, thus forming a Fabry-Pérot resonator, as shown in **Figure 9(b)**. Therefore, an ARROW is formed in HCF. However, due to two different infiltration materials, the IFN-γ solution and the NaCl solution, two ARROWs appear in HCF. At the wavelength of 1550.38 nm, the resonance condition of the ARROW for the optofluidic waveguide is achieved [12]. On the other hand, at the wavelength of 1557.86 nm, the resonance condition of the ARROW for the NaCl-infiltrated channel is achieved [13]. Hence, there are two resonance dips corresponding to two materials, which can be expressed as Eqs. (6)

> ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi *n*2 *op* � *n*<sup>2</sup> *air*

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi *n*2 *na* � *n*<sup>2</sup> *air* <sup>p</sup> <sup>þ</sup> *dcl*

*(a) Diagram of the dual-optofluidic waveguide ARROW and (b) the Fabry-Pérot resonator [12].*

þ *dcl*

� � q

*m*

� � q

*m*

where *m* is the resonance order, *λ<sup>o</sup>* and *λ<sup>n</sup>* are wavelengths of resonance dips for IFN-γ and NaCl solution, *dop* and *dcl* are diameters of the hole and thickness of the silica cladding, and *nair*, *nop*, *nna* and *nsilica* are RIs of the core, IFN-γ solution, NaCl

Due to the change of RI in the optofluidic waveguide [12], the immunoreaction between the aptamer and the IFN-γ could modulate the wavelength of the resonant dip for the IFN-γ infiltrated ARROW. However, the resonant wavelength dip is fixed because of the channel independence of NaCl-infiltrated resonator. On the other side, due to the similar thermos-optical coefficients of the NaCl and IFN-r, the wavelength shifts of two resonance dips corresponding to two ARROWs have the same response to the temperature fluctuation [12]. The response of the two resonance attenuation wavelength shifts corresponding to the two ARROWs to temperature fluctuation is the same. Therefore, a dual-optofluidic waveguide ARROW

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi *n*2 *silica* � *n*<sup>2</sup> *air*

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi *n*2 *silica* � *n*<sup>2</sup> *air* (6)

(7)

The cross-sectional schematic diagram of the optical fiber biosensor is shown in

**Figure 8(c)** [12].

and (7) [12, 13]:

**Figure 9.**

**20**

*λ<sup>o</sup>* ¼

*λ<sup>n</sup>* ¼

solution, and silica, respectively.

2 *dop*

2 *dop*

q

biosensor with temperature compensation is formed by interrogating and inquiring the wavelength interval between the two resonance dips of the dual-optofluidic flow waveguide ARROW [12, 13].

The biosensor of DR-ARROW was also tested [12]. The corresponding transmission spectra, **Figure 1A** is shown in Appendix [12]. The transmission spectrum of the ethanol and NaCl infiltrated the dual-optofluidic waveguide ARROW biosensor, **Figure 1A(a)** is shown in Appendix [12]. There are two resonance dips in the wavelength range of 1525–1565 nm. The resonance dips at 1545.58 and 1550.86 nm are consistent with the theoretical predictions of the ethanol-infiltrated Fabry-Pérot cavity (1545.78 nm) and the NaCl-infiltrated Fabry-Pérot cavity (1550.38 nm) [12]. Therefore, there will be two resonance dips if the two materials infiltrated Fabry-Pérot resonators at the same time. Different concentrations of ethanol solution are injected into the optofluidic waveguide channel, and the corresponding RI changes from 1.3568 to 1.3622 RIU. When the temperature is 20° C, the wavelength shift of the ARROW of dual-optofluidic waveguide with different RIs, **Figure 1A(b)** is shown in Appendix [12]. The wavelengths of two resonance attenuations for different RIs, **Figure 1A(C)** is shown in Appendix [12]. In addition, the wavelength spacing of the two resonance dips, **Figure 1A(d)** is shown in Appendix [12]. In this experiment, if the resolution of OSA is 0.02 nm, the sensitivity of RI response can reach �1413 nm/RIU [12].

In addition, the effect of temperature on the biosensor was investigated by experiments [12]. The transmission spectra of the biosensor at different temperatures from 20 to 80°C are shown in **Figure 10(a)** [12]. At different temperatures, the two resonance decays shift to longer wavelengths at the same time. However, due to the same temperature response of the two ARROWs, the wavelength interval is maintained at a standard change of 0.02 nm, as shown in **Figure 10(b)** [12]. Hence, the dual-optofluidic waveguide ARROW biosensor is not sensitive to temperature by interrogating the wavelength interval [12].

#### **3.4 The hybrid antiresonant reflecting optical waveguide sensor**

Most of the ARROW-based fiber sensors only rely on the working principle of the ARROW. In recent years, the fiber optic sensor of the hybrid antiresonant reflecting optical waveguide (H-ARROW) has been researched. Besides the ARROW, another mechanism was also formed in the fiber, making a hybrid

*(a) Wavelength shifts at different temperature from 20 to 80°C and (b) wavelength of resonance dips and the wavelength interval [12].*

**Figure 11.**

*(a) The cross section of single-hole twin eccentric core fiber and (b) three-dimensional diagram of single-hole twin eccentric core fiber [15].*

mechanism in a single ARROW-based fiber sensor [14, 15]. The two different mechanisms could measure different parameters dependently, which increase the multifunction of the ARROW-based fiber sensor significantly. In this section, a curvature ARROW-based fiber sensor with hybrid mechanism is introduced as an example [15].

*Tanti* ¼ *A*

*The cross-sectional microscope images of the single-hole twin eccentric core fiber [15].*

*The Antiresonant Reflecting Optical Waveguide Fiber Sensor*

*DOI: http://dx.doi.org/10.5772/intechopen.93345*

*<sup>λ</sup>anti* <sup>¼</sup> <sup>2</sup>*<sup>d</sup> m*

The sensor structure also produces MZ interference rather than the

*TMZi* <sup>¼</sup> *Bi* cos <sup>2</sup> *<sup>π</sup>*

be obtained by the following equation as Eq. (9) [15, 32]:

fiber cladding and the air, respectively.

ence can be normalized as Eq. (10) [15, 32]:

modes.

**23**

**Figure 12.**

*F* sin <sup>2</sup> <sup>2</sup>*<sup>π</sup>*

<sup>1</sup> <sup>þ</sup> *<sup>F</sup>* sin <sup>2</sup> <sup>2</sup>*<sup>π</sup>*

where *F* represents the fringe finesse coefficient of the multiple-beam interferometer. λ and n(λ) are the wavelengths of the spectrum and effective RI of the cladding, respectively. A and *l* are the intensity coefficients of the whole antiresonant effect and optical path of the antiresonant beams. In addition, the wavelength at resonance can

q

where *d* is the thickness of the single-hole twin eccentric core fiber cladding, and *m* is the resonance order. *n*<sup>1</sup> and *n*<sup>2</sup> are the RIs of the single-hole twin eccentric core

antiresonance effect. As shown in **Figures 11(a)** and **(b)**, the in-line MZ structure forms several modes, including core mode, low-order mode, and high-order cladding mode. The dominant interference is formed between the core mode and the low-order cladding mode. Therefore, the transmission of the multimode interfer-

where *Bi* is the intensity coefficient of the comb spectrum, Δ*ni* is the effective RI difference between the fiber core mode and cladding modes, *L* is the physical length of the special fiber cladding, and *i* represents the order of the cladding

A curvature experiment is conducted to investigate the sensing properties [15]. The test results are shown in **Figure 13**. The sensing characteristics are investigated by the curvature experiment [15]. The test results are shown in **Figure 13**. The curvature variation can be derived from 0.94 to 2.10 m�<sup>1</sup> according to the equation of *Rsin L*ð Þ¼ *=2R* ð Þ *L* � *d =*2 [15]. In this experiment, fitted resonant wavelength

*<sup>λ</sup>* <sup>n</sup>ð Þ*<sup>λ</sup> <sup>l</sup>* � �

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi *n*2 <sup>1</sup> � *n*<sup>2</sup> 2

*<sup>λ</sup>* � <sup>Δ</sup>*ni* � *<sup>L</sup>*

� � (10)

*<sup>λ</sup>* <sup>n</sup>ð Þ*<sup>λ</sup> <sup>l</sup>* � � (8)

(9)

Optical fiber curvature sensors have been widely used in structural health monitoring and distributed sensing fields, such as buildings, towers, and bridges [15, 29]. The optical fiber curvature sensor has the advantages of small volume, high sensitivity, and no electromagnetic interference [30, 31]. Here, an all-fiber vibration sensor is based on H-ARROW, through the integrated antiresonance mechanism and in-line Mach Zehnder interference (MZI) [32]. The schematic construction of the proposed curvature sensor is given in **Figure 11** [15]. The singlehole double-core fiber is characterized by replacing the core with a large air hole, one of which is suspended on the inner surface of the cladding. As shown in **Figure 11(a)**, the other core is asymmetrically distributed outside the air hole. As can be seen from **Figure 11(b)**, for the curvature fiber, Core 1 is suspended in the air hole in the middle of the hollow-core fiber, and Core 2 is in the cladding of the hollow-core fiber [15].

The principle of curvature sensor of H-ARROW is analyzed [15]. According to its structure, the single-hole dual-core fiber is characterized by replacing the core with a large air hole, one of which is suspended on the inner surface of the cladding, as shown in **Figure 12** [15]. According to the working principle of the single-hole double-eccentric core fiber, the distribution of light field in the whole fiber is of great significance [15]. A section of a 2.6 mm single-hole double-eccentric core fiber is fused between two single-mode fibers. It is well known that when a beam travels between different media, it will reflect and refract. Specifically, for the beams propagating from the optical dense medium to the optical thin film medium, only when the incident angle is less than the critical incident angle, the two effects exist at the same time [15].

The transmission spectrum of the optical fiber sensor is controlled by two effects: antiresonance and in-line MZI [15]. It should be noted that the backscattered beam undergoes multiple reflections in the cladding. As a result, Fabry-Pérot resonators are formed in a silicon cladding. The antiresonance effect of the single-hole double eccentric core fiber can be regarded as the reflection type Fabry-Pérot interferometer. Therefore, the transmission of the antiresonance effect can be expressed as Eq. (8) [15, 32]:

*The Antiresonant Reflecting Optical Waveguide Fiber Sensor DOI: http://dx.doi.org/10.5772/intechopen.93345*

**Figure 12.** *The cross-sectional microscope images of the single-hole twin eccentric core fiber [15].*

$$T\_{anti} = A \frac{F \sin^2\left(\frac{2\pi}{\lambda} \mathbf{n}(\lambda)l\right)}{1 + F \sin^2\left(\frac{2\pi}{\lambda} \mathbf{n}(\lambda)l\right)}\tag{8}$$

where *F* represents the fringe finesse coefficient of the multiple-beam interferometer. λ and n(λ) are the wavelengths of the spectrum and effective RI of the cladding, respectively. A and *l* are the intensity coefficients of the whole antiresonant effect and optical path of the antiresonant beams. In addition, the wavelength at resonance can be obtained by the following equation as Eq. (9) [15, 32]:

$$
\lambda\_{anti} = \frac{2d}{m} \sqrt{n\_1^2 - n\_2^2} \tag{9}
$$

where *d* is the thickness of the single-hole twin eccentric core fiber cladding, and *m* is the resonance order. *n*<sup>1</sup> and *n*<sup>2</sup> are the RIs of the single-hole twin eccentric core fiber cladding and the air, respectively.

The sensor structure also produces MZ interference rather than the antiresonance effect. As shown in **Figures 11(a)** and **(b)**, the in-line MZ structure forms several modes, including core mode, low-order mode, and high-order cladding mode. The dominant interference is formed between the core mode and the low-order cladding mode. Therefore, the transmission of the multimode interference can be normalized as Eq. (10) [15, 32]:

$$T\_{MZi} = B\_i \cos^2\left(\frac{\pi}{\lambda} \cdot \Delta n\_i \cdot L\right) \tag{10}$$

where *Bi* is the intensity coefficient of the comb spectrum, Δ*ni* is the effective RI difference between the fiber core mode and cladding modes, *L* is the physical length of the special fiber cladding, and *i* represents the order of the cladding modes.

A curvature experiment is conducted to investigate the sensing properties [15]. The test results are shown in **Figure 13**. The sensing characteristics are investigated by the curvature experiment [15]. The test results are shown in **Figure 13**. The curvature variation can be derived from 0.94 to 2.10 m�<sup>1</sup> according to the equation of *Rsin L*ð Þ¼ *=2R* ð Þ *L* � *d =*2 [15]. In this experiment, fitted resonant wavelength

mechanism in a single ARROW-based fiber sensor [14, 15]. The two different mechanisms could measure different parameters dependently, which increase the multifunction of the ARROW-based fiber sensor significantly. In this section, a curvature ARROW-based fiber sensor with hybrid mechanism is introduced as an

*(a) The cross section of single-hole twin eccentric core fiber and (b) three-dimensional diagram of single-hole*

*Electromagnetic Propagation and Waveguides in Photonics and Microwave Engineering*

nism and in-line Mach Zehnder interference (MZI) [32]. The schematic

Optical fiber curvature sensors have been widely used in structural health monitoring and distributed sensing fields, such as buildings, towers, and bridges [15, 29]. The optical fiber curvature sensor has the advantages of small volume, high sensitivity, and no electromagnetic interference [30, 31]. Here, an all-fiber vibration sensor is based on H-ARROW, through the integrated antiresonance mecha-

construction of the proposed curvature sensor is given in **Figure 11** [15]. The singlehole double-core fiber is characterized by replacing the core with a large air hole, one of which is suspended on the inner surface of the cladding. As shown in **Figure 11(a)**, the other core is asymmetrically distributed outside the air hole. As can be seen from **Figure 11(b)**, for the curvature fiber, Core 1 is suspended in the air hole in the middle of the hollow-core fiber, and Core 2 is in the cladding of the

The principle of curvature sensor of H-ARROW is analyzed [15]. According to its structure, the single-hole dual-core fiber is characterized by replacing the core with a large air hole, one of which is suspended on the inner surface of the cladding, as shown in **Figure 12** [15]. According to the working principle of the single-hole double-eccentric core fiber, the distribution of light field in the whole fiber is of great significance [15]. A section of a 2.6 mm single-hole double-eccentric core fiber is fused between two single-mode fibers. It is well known that when a beam travels between different media, it will reflect and refract. Specifically, for the beams propagating from the optical dense medium to the optical thin film medium, only when the incident angle is less than the critical incident angle, the two effects exist

The transmission spectrum of the optical fiber sensor is controlled by two

backscattered beam undergoes multiple reflections in the cladding. As a result, Fabry-Pérot resonators are formed in a silicon cladding. The antiresonance effect of the single-hole double eccentric core fiber can be regarded as the reflection type Fabry-Pérot interferometer. Therefore, the transmission of the antiresonance effect

effects: antiresonance and in-line MZI [15]. It should be noted that the

example [15].

**Figure 11.**

*twin eccentric core fiber [15].*

hollow-core fiber [15].

at the same time [15].

**22**

can be expressed as Eq. (8) [15, 32]:

**Conflict of interest**

**Appendix**

**Figure 1A.**

**25**

*with different RIs [12].*

The authors declare no conflicts of interest.

*The Antiresonant Reflecting Optical Waveguide Fiber Sensor*

*DOI: http://dx.doi.org/10.5772/intechopen.93345*

*(a) Transmission spectrum of the dual-optofluidic waveguide ARROW biosensor, (b) wavelength shifts with different RI, (c) relationship between the wavelengths of resonance dips and RI, and (d) wavelength interval*

**Figure 13.**

*(a) The intensity variation of the actual resonant wavelength with the curvature increased and (b) the intensity variation of the Gaussian fits resonant wavelength (dip2) with curvature increasing from 0.94 to 2.1 m*�*<sup>1</sup> [15].*

(dip2) is selected to monitor the curvature variation trend, corresponding to the resonant wavelength of 1570 nm [15]. The intensity of the actual wavelength decreases as the curvature increases, as shown in **Figure 13**. The intensity of the actual resonant wavelength decreases as the curvature increases, as shown in **Figure 13(a)** [15]. The actual wavelength circled by the red ellipse is about 1571 nm, and the inset is the enlarged view of the intensity variation [15]. The actual wavelength circled by the red ellipse is about 1571 nm, and the illustration is an enlarged picture of intensity change [15]. **Figure 13(b)** reflects that there is also only intensity variation without wavelength shift. The Gaussian fitting resonant wavelength of dip2 undergoes intensity decreasing when the curvature increases from 0.94 to 2.10 m�<sup>1</sup> [15].

#### **4. Conclusion**

In summary, this chapter introduces the optical fiber sensors based on ARROW. According to the working principle, the optical fiber sensors based on ARROW consist of the single layer, double layers, double resonators, and hybrid mechanism. Various optical fiber sensors based on ARROW have been introduced in this chapter with the aforementioned working principle, including the fiber optic vibration sensor, humidity sensor, strain sensor, temperature sensor, magnetic field sensor, biosensor, etc. The optical fiber sensors based on ARROW could enhance the interaction between the guided light and sensitive material, simplify the complexity of the sensor configuration, and increase the multifunctional performance of the fiber sensor. Especially, many long-standing challenges in the fiber optic sensor can be solved through the working principle of the ARROW, including the temperature cross-talk compensation, distribution localization, and optofluidic biosensing. In general, the optical fiber sensors based on ARROW have advantages, such as compact structure, high sensitivity, large dynamic range, and high stability, which appear to have potential applications in researches of structure health monitoring, oil exploiting, and biology detection.

#### **Acknowledgements**

The authors acknowledge the China National Key R&D Program (No. 2019YFA0706304) and the National Natural Science Foundation of China (Nos. 61835002, 61675033, 61727817, and 61601436).

*The Antiresonant Reflecting Optical Waveguide Fiber Sensor DOI: http://dx.doi.org/10.5772/intechopen.93345*
